State and parameter estimation approach to monitoring AGR nuclear core

This work concerns with the problem of monitoring an Advanced Gas-cooled Nuclear Reactor (AGR) core. This plant (figure 1) makes use of the heat given by the nuclear efficient reaction to produce electricity by means of steam turbines. These are driven by steam, which is heated, from the AGR gas using a heat exchanger. One of the advantages of a gas cooled reactor is the high temperature that the gas can achieve so that when it is used in conjunction with the heat exchanger and steamed turbine the thermal efficiency is very high

Condition monitoring of an advanced gas-cooled nuclear reactor core

A critical component of an advanced gas-cooled reactor station is the graphite core. As a station ages, the graphite bricks that comprise the core can distort and may eventually crack. Since the core cannot be replaced, the core integrity ultimately determines the station life. Monitoring these distortions is usually restricted to the routine outages, which occur every few years, as this is the only time that the reactor core can be accessed by external sensing equipment. This paper presents a monitoring module based on model-based techniques using measurements obtained during the refuelling process. A fault detection and isolation filter based on unknown input observer techniques is developed. The role of this filter is to estimate the friction force produced by the interaction between the wall of the fuel channel and the fuel assembly supporting brushes. This allows an estimate to be made of the shape of the graphite bricks that comprise the core and, therefore, to monitor any distortion on them

Who uses foodbanks and why? Exploring the impact of financial strain and adverse life events on food insecurity

Background Rising use of foodbanks highlights food insecurity in the UK. Adverse life events (e.g. unemployment, benefit delays or sanctions) and financial strains are thought to be the drivers of foodbank use. This research aimed to explore who uses foodbanks, and factors associated with increased food insecurity. Methods We surveyed those seeking help from front line crisis providers from foodbanks (N = 270) and a comparison group from Advice Centres (ACs) (N = 245) in relation to demographics, adverse life events, financial strain and household food security. Results About 55.9% of foodbank users were women and the majority were in receipt of benefits (64.8%). Benefit delays (31.9%), changes (11.1%) and low income (19.6%) were the most common reasons given for referral. Compared to AC users, there were more foodbank users who were single men without children, unemployed, currently homeless, experiencing more financial strain and adverse life events (P = 0.001). Food insecurity was high in both populations, and more severe if they also reported financial strain and adverse life events. Conclusions Benefit-related problems appear to be a key reason for foodbank referral. By comparison with other disadvantaged groups, foodbank users experienced more financial strain, adverse life events, both increased the severity of food insecurity

Nonlinear model-based condition monitoring of advanced gas-cooled nuclear reactor cores

The graphite core is one critical component in gascooled nuclear reactors and it ages and degrades over time. As a result, the graphite core can dictate the life-time of a reactor in a nuclear power station. To support the safety cases and ensure the continued safe operation of an advanced gas-cooled reactor (AGR) nuclear plant, it is important to closely monitor the condition of its reactor graphite core to maintain the integrity throughout the life of the reactor. Toward this end, the fuel grab load trace (FGLT) measurements are currently used as main information sources to infer the core condition. Due to the fact that the FGLTs are masked by many effects in the refuelling process, the first principles models for nuclear refuelling process are promising to separate the information of interests to core condition from the masked FGLT measurements. To reliably and accurately obtain the unknown parameters existing in the developed first principles model for model-based condition monitoring of AGR nuclear graphite cores, this paper presents a nonlinear system identification approach. In this approach, a nonlinear first principles model is first developed to describe the refuelling process. A friction model is then investigated to mathematically deal with the frictional effects. The aerodynamic force is also modelled separately. Finally, the Trust- Region Reflective Newton method is used to find the optimal parameters in the nonlinear refuelling model. The real-world data from an AGR nuclear power plant is employed to demonstrate the effectiveness of the proposed nonlinear system identification approach for nonlinear model-based condition monitoring of graphite core

Roll reduction and course keeping for the ship moving in waves with factorized NGMV control

A factorized Nonlinear Generalized Minimum Variance (NGMV) control law is developed for a combined roll and yaw motion compensation using rudders and fins. The nonlinear model used for control design includes the non-minimum phase interaction from rudder to roll motion, and the dynamics from fins to yaw motion. This controller is developed using the polynomial approach to ensure that the non-minimum phase system remains stable in closed-loop. The effectiveness of the approach is demonstrated on a simulated nonlinear ship model

Nonlinear Optimal Generalized Predictive Functional Control applied to quasi-LPV model of automotive electronic throttle

A Nonlinear Optimal Generalized Predictive Functional Control algorithm is presented for the control of quasi linear parameter varying state-space systems. A scalar automotive electronic throttle body is simulated to demonstrate typical results. The controller structure is specified in a restricted structure form including a set of pre-specified linear transfer-functions and a vector of gains that are found to minimize a GPC cost-index. This approach enables a range of classical controller structures to be used in the feedback loop such as extended PI, PID or of a more general transfer-function form. The controller is introduced along with a dynamic cost-weighting tuning future. A simulation is used to validate the performance of the restricted structure controller for regulation and tracking problems assessed against automotive performance standards

Thin film tribology of pharmaceutical elastomeric seals

The primary purpose of valve seals in inhalation and other drug dispensing devices is to inhibit leakage of highly volatile formulation from pressurised canisters. This requirement often conflicts with smooth operation of valves because of poor lubrication of seals. The repercussions of this can be variability in dispensed dose as well as loss of prime and gradual wear of seals. Although a good volume of literature is available for general purpose o-ring seals, the characteristic behaviour of those used in pharmaceutical devices deviate from this significantly. The paper studies tribology of such seals, subjected to global fitment and canister pressure deformation and localised conjunctional elastohydrodynamic pressures. It is shown that ideally smooth seals would operate under iso-viscous elastic (soft EHL) regime of lubrication. However, the predicted ultra-thin films are insufficient to ensure fluid film lubrication because of rough micro-scale nature of elastomeric seal surface and poor lubricity of the usual bio-compatible formulations. The paper also shows that siliconisation of elastomeric contacting surface only marginally improves its tribological performance